Gen III Goodies
Rich Wojnar, via CarCraft.com: I am e-mailing you about the past two articles you wrote about the budget Chevy Gen III 6.0L engine build, the latest titled "550 hp for Under $4,900" (May '07).
My reason for this letter is to see if you have performed any additional tests or have any new theories. Just before you guys wrote these articles, I had a 6.0L already sitting in the garage! So I decided to get that project underway. And I am currently researching a head and cam package for it. It will definitely be carb'd, but I would like to choose a good set of heads (really liked the write-up of the L92 heads) and a nasty cam.
To make a long story short, I was hoping that you could share anything you have found out with your trials thus far, or if you have tried any more combos. would appreciate any feedback you are willing to share!
Jeff Smith: Have you been reading our mail, Rich? You're right on target. Our idea is to buy a basic LQ4 or LQ9 Gen III truck engine. We've already been pricing these engines and recently ran across two on eBay that were selling for $700 from an upstate New York recycler. This is a good price, but we didn't go for it because we'd prefer to find an engine a little closer to home that we can check out in person. We dug into the research bin a little deeper to see what it would cost if we started out with a brand-new iron 6.0L Gen III block that's available from GM.
Performance Parts. This block was righteously priced at $700, but by the time we added up all the little parts the engine needed that we don't have, like an oil pan, front and rear covers, and a ton of metric fasteners, it looked like the price would be about the same.
Here's our plan. Buy a used 6.0L iron-block motor, line up a 4.00-inch steel stroker crank, rods, and forged piston assembly from Scat or Eagle that includes a good forged 4.030-inch piston from Diamond, Mahle, or SRP. This will produce a 408-cid package. We bolt all the parts from our last 6.0L engine package onto this larger-displacement engine. The story you mention, "550 hp for Under $4,900," configured our truck LQ4 364ci cast-piston short-block with a Comp Cams XR281HR hydraulic roller cam with 228/230 degrees at 0.050 with 0.571/0.573-inch lift numbers and a 112-degree lobe separation angle. We matched that cam to a set of bone-stock, out-of-the-box L92 production Gen III aluminum heads that just happened to have a 2.16-inch intake valve and flowed 302 cfm at 0.500-inch lift and 332 at 0.600-inch. Yeoowsaaah!
The package in the May story made 551 hp at 6,800 rpm with peak torque of 464 lb-ft at a high 5,400 rpm. The giant L92 heads pushed the powerband way up there where you'd really need a deep gear to take advantage of all that power, but it's there for the taking. We've also heard through our GM contacts that a typical LQ4 cast-piston engine would probably be cracking pistons if it spent too much time at that rpm level. That's why we decided to go with a good steel crank, 4340 I-beam rods, and forged pistons. As for power, I did a little simple math to point us in the right direction. With 551 hp from a 364ci engine, that comes out to an excellent 1.51 hp/ci. We're making some assumptions, but for grins I multiplied 408 ci times 1.51, which gives us a stout 616 hp. Plus, the larger cubic inches will automatically make more torque and should bring the peak-horsepower rpm point down to 6,500. All of this is good, but it's not cheap. The rotator will be around $2,600 because the prices for Gen III engine parts have yet to settle to Gen I levels. The L92 heads are a blessing since a pair of these heads with the rockers and other pieces is a little over $1,000. Get it built and you can expect to have somewhere in the neighborhood of $8,000 invested, including an intake, carb, the MSD ignition conversion for a distributorless ignition system, and a good set of headers as part of the recipe.